What Is The Difference Between AHU And FCU?

The world of commercial and industrial chillers is full of parts and devices, and it is always helpful to know what they are. Here at J.C Younger, we believe in keeping customers informed of everything one might need to know, so we bring you this post, which will cover two terms that may crop up when you are thinking about your business’s cooling needs. These terms are AHU and FCU.


AHU stands for ‘air handling unit,’ and is used to describe any device that handles air. This includes devices that transport, heat, or cool it. They are generally large machines that are part of a HVAC system and often take air from outside, condition it, and blow it into the building. Since they can handle a lot of air, they are often used to cool or heat whole buildings. If they are taking in 100% outside air and don’t recirculate any indoor air, they are called makeup air units, or MAU’s. The air handling units you see on roofs and outside of buildings are called either packaged units or rooftop units.


FCU stands for fan coil unit, and refers to a self-contained unit composed of a fan and a heating or cooling heat exchanger. The fans in FCU’s are, unlike in air handling units, put inside the same space as the fan coil unit. FCU’s can be controlled by a manual switch or a thermostat. As a rule, they are small units that re-circulate air through a building instead of taking air from outside.

Smaller fan coil units are sometimes called terminal units because they can be seen as little air handling units for single rooms. These units can be either mounted on the ceiling of a room or on the floor.

The Differences Between AHU’s and FCU’s

  1. AHU’s are often used outside, especially as rooftop units.
  2. FCU’s have only one fan, whereas AHU’s can have multiple fans
  3. AHU’s often have different controls for parts of the system, for instance they might have temperature sensors, actuators, and humidity sensors.
  4. AHU’s are more complex and can have sections for humidifying and reheating. They often have vibration isolators, mixing chambers, and other components. Since they often take air from outside, they almost always have a filter of some sort in the first section of the device so that the debris from the air doesn’t contaminate the other sections.
  5. FCU’s are generally used for controlling the space where they are installed. AHU’s are part of a larger system.
  6. FCU’s don’t generally use ductwork to cool or heat air. The fan pulls the air over the coil.
  7. FCU’s can handle water.
  8. Air handler units normally put their fans at their ends or where the ducts originate in order to accommodate the many other moving parts that are part of the system.

J.C Younger has been manufacturing and remanufacturing chillers for commercial applications since 1956, and we are very familiar with the intricacies of air handling units and fan coil units. Our company carries chillers that you can rent from anywhere from a week to long term R&D applications, and we have some you can buy.

We have technicians to help troubleshoot chillers, total chiller packages to ensure that you have all your needs met, pre-mixed glycol, and technical know-how to help you pick the right chiller for your needs. We can pick the right size chiller based on the information you give us about your needs. All this means that if you feel that your company needs to rent or buy a chiller, we will be able to meet your needs. Please contact us. We’ll be glad to help.


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